See if it's poly limit related, especially if you have lods, remove all other doors, bonnet and try your boot again. If with only your boot it still does same crash, try following...

it could be collision related since they lots of the time are too sensitive...try using original collision model, or use whole original boot everything including collision from something, drag it with dummy affecting children close to location where you want your boot dummy and test it. If it will work adjust your dummy location, replace model with yours, reshape collision to your model.